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Publication numberUS6380050 B1
Publication typeGrant
Application numberUS 09/616,725
Publication dateApr 30, 2002
Filing dateJul 14, 2000
Priority dateJul 14, 1999
Fee statusLapsed
Also published asCN1156893C, CN1281247A
Publication number09616725, 616725, US 6380050 B1, US 6380050B1, US-B1-6380050, US6380050 B1, US6380050B1
InventorsWang Nang Wang, Yurii Georgievich Shreter, Yurii Toomasovich Rebane
Original AssigneeArima Optoelectronics Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of epitaxially growing a GaN semiconductor layer
US 6380050 B1
Abstract
A method for growth of strain free epitaxial layers of semiconductors on highly lattice mismatched substrates is suggested using a buffer layer with a solid-liquid phase transition to accommodate high mismatch between substrate and semiconductor.
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Claims(6)
What is claim is:
1. A method of epitaxially growing a GaN semiconductor layer on a highly mismatched substrate using a buffer layer with a solid-liquid phase transition comprising:
the epitaxial growth on the substrate of the buffer layer at a temperature lower than the melting temperature of the buffer layer;
the epitaxial growth on the buffer layer at a temperature lower than the melting temperature of the buffer layer of a protective layer with a melting temperature higher than the growth temperature of the GaN semiconductor layer to be epitaxially grown; and
the epitaxial growth on the protective layer at a temperature higher than the melting temperature of the buffer layer of the epitaxial GaN semiconductor layer with a thickness greater than the thickness of the protective layer.
2. A method according to claim 1 wherein the buffer layer is one of a metal, a metal alloy, a semiconductor alloy, a metal-semiconductor alloy and an ionic crystal of groups I-VII or II-VI.
3. A method according to claim 1 wherein the buffer layer is one of Al, Cu, Mg, Pb, Au, Ag and their alloys, the substrate is one of sapphire and SiC.
4. A method according to claim 1 wherein the protective layer is one of Mgo, Al2O3, AlN, GaN, InN and their alloys, the substrate is one of sapphire and SiC and the buffer layer is one of epitaxial AlN, GaN, InN and their alloys.
5. A method according to claim 1 wherein the buffer layer has a thickness from 5 Å to 500 Å.
6. A method according to claim 1 wherein the protective layer has a thickness from 5 Å to 500 Å.
Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of epitaxially growing a GaN semiconductor layer on a highly lattice mismatched substrate.

2. Description of the Prior Art

The epitaxial growth of a semiconductor on a highly mismatched substrate results in extremely strained semiconductor layers. This strain gives rise to the formation of many extended defects such as dislocations, grain boundaries, stacking faults, inversion domains, and is generally responsible for the poor quality of grown semiconductor layers. Buffer layers have been used for several decades for strain reduction and improving the quality of grown semiconductor layers. Usually, buffer layers are made of solid polycrystalline or amorphous semiconductors. Such buffer layers allow the elimination of up to 90% of the strain.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a growth method that allows the substantial elimination of the strain resulting from high mismatch between the lattice parameters of a semiconductor and a substrate on which the semiconductor is grown.

According to the present invention, there is provided a method of epitaxially growing a GaN semiconductor layer on a highly mismatched substrate using a buffer layer with a solid-liquid phase transition comprising:

the epitaxial growth on the substrate of the buffer layer at a temperature lower than the melting temperature of the buffer layer;

the epitaxial growth on the buffer layer at a temperature lower than the melting temperature of the buffer layer of a protective layer with a melting temperature higher than the growth temperature of the GaN semiconductor layer to be epitaxially grown; and

the epitaxial growth on the protective layer at a temperature higher than the melting temperature of the buffer layer of the epitaxial GaN semiconductor layer with a thickness greater than the thickness of the protective layer.

The growth of the epitaxial GaN semiconductor layer occurs on the thin protective layer which maintains the flatness of the liquid buffer layer and protects it from formation of liquid droplets on the substrate surface.

Since the protective layer is thin and weakly mechanically coupled to the substrate via the thin liquid buffer layer, it serves as a compliant substrate for the epitaxial GaN semiconductor layer.

Thus, the use of a buffer layer with solid-liquid phase transition allows the growth of high quality strain-free epitaxial semiconductor layers on highly mismatched substrates.

The buffer layer could be one of a metal, a metal alloy, a semiconductor alloy, a metal-semiconductor alloy and an ionic crystal of groups I-VII or II-VI.

The buffer layer could be one of Al, Cu, Mg, Pb, Au, Ag and their alloys, the substrate being one of sapphire and SiC.

The buffer layer could be one of Al, Cu, Mg, Pb, Au, Ag and their alloys, the substrate being one of sapphire and SiC.

The protective layer could be one of MgO, Al2O3, AlN, GaN, InN and their alloys, the substrate being one of sapphire and SiC and the buffer layer being one of epitaxial AlN, GaN, InN and their alloys.

The buffer layer preferably has a thickness from 5 Å to 500 Å.

The protective layer preferably has a thickness from 5 Å to 500 Å.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a-d illustrate stages in examples of methods according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1a-d show the principal stages of the growth of an epitaxial semiconductor layer using a buffer layer with a solid-liquid phase transition in each of the examples.

At a first stage (see FIG. 1a), a buffer 2 layer with a thickness from 5 Å to 500 Å is epitaxially grown on a substrate 31 at a temperature lower than its melting temperature.

At a second stage (see FIG. 1b), a protective layer 3 with a thickness from 5 Å to 500 Å and a melting temperature higher than the growth temperature of the epitaxial semiconductor layer is epitaxially grown on the buffer layer 2 at a temperature lower than the melting temperature of the buffer layer 2.

At the beginning of a third stage, temperature is raised to the growth temperature of the epitaxial semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick epitaxial GaN semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

The use of a buffer layer with a solid-liquid phase transition allows the growth of high quality strain free epitaxial semiconductor layers on highly mismatched substrates.

Examples of the above will now be described.

Example 1

At the first stage (see FIG. 1a), the buffer layer 2 is of Mg with a thickness of 100 Å, and is epitaxially grown on a sapphire substrate 1 at a temperature of 600 C.

At the second stage (see FIG. 1b), the protective layer 3 is of MgO with a thickness of 50 Å and is epitaxially grown on the buffer layer 2 at a temperature of 600 C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1100 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Example 2

At the first stage (see FIG. 1a), the buffer layer 2 is of A1 with a thickness of 100 Å and is epitaxially grown on a sapphire substrate 1 at a temperature of 600 C.

At the second stage (see FIG. 1b), the protective layer 3 is of Al2O3 with a thickness of 100 Å and is epitaxially grown on the buffer layer 2 at a temperature of 600 C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1150 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Example 3

At the first stage (see FIG. 1a), the buffer layer 2 is of Al with a thickness of 100 Å and is epitaxially grown on a sapphire substrate 1 at a temperature of 600 C.

At the second stage (see FIG. 1b), the protective layer 3 is of AlN with a thickness of 100 Å and is epitaxially grown on the buffer layer 2 at a temperature of 600 C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1150 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Example 4

At the first stage (see FIG. 1a), the buffer layer 2 is of NaF with a thickness of 200 Å and is epitaxially grown on a sapphire substrate 1 at a temperature of 800C.

At the second stage (see FIG. 1b), the protective layer 3 is of GaN with a thickness of 200 Å is epitaxially grown on the buffer layer 2 at a temperature of 600C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1100 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Example 5

At the first stage (see FIG. 1a), the buffer layer 2 is made of an alloy Ag0.5Pb0.5 (50% silver and 50% lead) with a thickness of 200 Å and is epitaxially grown on a sapphire substrate 1 at a temperature of 600C.

At the second stage (see FIG. 1b), the protective layer 3 is of AlN with a thickness of 200 Å and is epitaxially grown on the buffer layer 2 at a temperature of 600C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1150 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Example 6

At the first stage (see FIG. 1a), the buffer layer 2 is made of an alloy Cu0.3Pb0.7 (30% copper and 70% lead) with a thickness of 200 Å and is epitaxially grown on a sapphire substrate 1 at a temperature of 800C.

At the second stage (see FIG. 1b), a protective layer of AlN with a thickness of 200 Å is epitaxially grown on the buffer layer 2 at a temperature of 800C.

At the beginning of the third stage, temperature is raised to the growth temperature of 1150 C. for a GaN semiconductor layer. The temperature rise causes melting of the buffer layer 2 and the protective layer 3 releases strain to produce the structure shown in FIG. 1c.

Then, a thick GaN epitaxial semiconductor layer 4 is grown on the protective layer 3. The thickness of the epitaxial semiconductor layer 4 is greater than the thickness of the protective layer 3. The protective layer 3 serves as a compliant substrate for the epitaxial semiconductor layer 4 since it is weakly coupled to the substrate 1 via the thin liquid buffer layer 2 and adjusts its lattice parameter to the lattice parameter of the thick epitaxial semiconductor layer 4.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US6107113 *Dec 9, 1997Aug 22, 2000France TelecomMaking stacks of metamorphic layers of semiconductor material having lattice mismatches of several percent between one another or relative to the substrate
EP0848414A1 *Dec 8, 1997Jun 17, 1998France TelecomStress relaxation method of a strained film by fusion of an interfacial layer
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7354619 *Sep 20, 2004Apr 8, 2008Commissariat A L'energie AtomiqueProtection of the SiC surface by a GaN layer
US7951685 *Sep 14, 2007May 31, 2011Sumitomo Chemical Company, LimitedMethod for manufacturing semiconductor epitaxial crystal substrate
US20140138796 *Jan 27, 2014May 22, 2014SoitecStrain relaxation using metal materials and related structures
Classifications
U.S. Classification438/478, 257/E21.125, 257/E21.121
International ClassificationC30B29/04, H01L21/205, C30B29/38, H01L21/20, H01L21/208
Cooperative ClassificationH01L21/0254, H01L21/02491, H01L21/0237, H01L21/02502, H01L21/02439, H01L21/02458, H01L21/0242, H01L21/02378
European ClassificationH01L21/02K4A1A2, H01L21/02K4C1B1, H01L21/02K4B1B1, H01L21/02K4A1, H01L21/02K4B1L, H01L21/02K4B5L2, H01L21/02K4B1, H01L21/02K4A1J
Legal Events
DateCodeEventDescription
Jun 17, 2014FPExpired due to failure to pay maintenance fee
Effective date: 20140430
Apr 30, 2014LAPSLapse for failure to pay maintenance fees
Dec 6, 2013REMIMaintenance fee reminder mailed
Jun 27, 2006FPExpired due to failure to pay maintenance fee
Effective date: 20060430
Nov 16, 2005REMIMaintenance fee reminder mailed
Oct 2, 2000ASAssignment
Owner name: ARIMA OPTOELECTRONICS CORPORATION, TAIWAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WANG, WANG NANG;SHRETER, YURII GEORGIEVICH;REBANE, YURIITOOMASOVICH;REEL/FRAME:011207/0962
Effective date: 20000720
Owner name: ARIMA OPTOELECTRONICS CORPORATION 6TH FLOOR, NO. 3